Hollow-core optical fibers

A hollow-core optical fiber comprising:

• a hollow core extending along a central longitudinal axis of the hollow-core optical fiber;
• a substrate, the substrate comprising a tubular shape and an inner surface surrounding the central longitudinal axis of the hollow-core optical fiber;
• and
• a plurality of cladding elements positioned between the hollow core and the substrate, each of the plurality of cladding elements extending in a direction parallel to the central longitudinal axis of the hollow-core optical fiber, each of the plurality of cladding elements comprising:
• a primary capillary, the primary capillary directly contacting the inner surface of the substrate and comprising an inner surface defining a cavity, and
• a plurality of nested capillaries positioned within the cavity, each of the plurality of nested capillaries directly contacting the inner surface of the primary capillary;
• wherein each nested capillary directly contacts at least one other nested capillary.